Find out what causes beach ball when running Sheepshaver

This is a very weird case and I’ve searched around in a lot of user forums, but nowhere was an answer or not even a vague explanation. So I’m hoping, someone here has an idea where to search.

I downloaded and setup Sheepshaver on my MacBook pro running the latest Catalina. No matter what I do, Sheepshaver hangs with a beach ball. (ROM file provided and valid.) Doing exact the same setup under another user or on another Mac, Sheepshaver runs fine. I have no firewall, no antivirus running or anything else that could restrict file or network access. I’ve checked permissions, ACLs, moved it to another location, re-downloaded the application and ROM file. No success. The only thing that works is running it via terminal and sudo. But that’s not the desired way.

So how would one analyze what’s causing a beach ball with an application, when the application itself doesn’t provide a log file?